Life events and depressiveness - the effect of adjustment for psychosocial factors, somatic health and genetic liability.

OBJECTIVE: To study the nature of the relationship of life events with depressiveness. METHOD: In 1990, 9947 Finnish adult twins aged 33-60 years participated in a questionnaire study, with no missing data on the analysed variables. The relationship between stressful life-events and depressiveness, based on Beck Depression Inventory (BDI) classified as normal, mild or moderate, was analysed using multinomial regression for all subjects with adjustment for the effect of age, sex, health status, social support, marital status, social class, and personality variables. These same factors were analyzed among 643 twin pairs discordant for depressiveness. RESULTS: High BDI score categories were strongly associated with stressful life events in all individuals and equally strongly within discordant twin pairs, both monozygotic and dizygotic. Poor somatic health and lack of social support also increased depressiveness. CONCLUSION: The effect of life events predicting depressiveness was independent of social support, somatic disease, sex and genetic liability.

Familial association between allergic disorders and depression in adult Finnish twins.

Clinical studies have shown a relationship between allergic disorders and depression, panic disorder, attention deficit/hyperactivity disorder, and social anxiety for a significant subset of patients with these disorders. The nature of the relationship, whether due to shared environmental or biologic vulnerabilities or as a result of the stress of chronic illness, has been less clear. By examining the covariance of atopic disorders and depressive symptoms in a community sample of monozygotic (MZ) and dizygotic (DZ) twins, the contribution of genetic and/or shared environmental etiological factors can be established. A Finnish sample of 1337 MZ and 2506 DZ twin pairs, ages 33-60 years, was sent questionnaires inquiring about history of asthma, eczema, and atopic rhinitis, as well as the Beck Depression Inventory (BDI). The nature of the covariation between twins of these symptoms was investigated by fitting competing genetic and environmental models. Within-person correlation between atopic symptoms and BDI was 0.103 (P < 0.001) for the total sample. Using the Mx statistical modeling program to fit the data to competing quantitative genetic models, the best fitting model estimated that 64% of the association between atopy and BDI was due to shared familial vulnerability, primarily additive genetic influences. Although the measures for allergic disorders and depression are crude, this study supports the hypothesis that there is a small shared genetic risk for atopic and depressive symptoms, and if replicated, may open research for common mechanisms between allergic and depressive disorders. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:146-153, 2000.

Magnetic fields of transmission lines and depression.

Electromagnetic fields have been suggested to contribute to the risk of depression by causing pineal dysfunction. Some epidemiologic studies have supported this possibility but have generally reported crude methods of exposure assessment and nonsystematic evaluation of depression. Using two available nationwide data sets, the authors identified from the Finnish Twin Cohort Study 12,063 persons who had answered the 21-item Beck Depression Inventory of self-rated depressive symptoms in 1990. The personal 20-year histories of exposure (i.e., distance and calculated annual average magnetic fields) before 1990 to overhead 110- to 400-kv power lines were obtained from the Finnish Transmission Line Cohort Study. The adjusted mean Beck Depression Inventory scores did not differ by exposure, providing some assurance that proximity to high-voltage transmission lines is not associated with changes within the common range of depressive symptoms. However, the risk of severe depression was increased 4.7-fold (95% confidence interval 1.70-13.3) among subjects living within 100 m of a high-voltage power line. This finding was based on small numbers. The authors recommend that attempts be made to strive for a better understanding of the exposure characteristics in relation to the onset and course of depression.